This invention relates generally to a fuser member, a method for fabricating the fuser member, and a method of fusing toner images in electrostatographic reproducing apparatus. In particular, the present invention relates to a fuser member which may preferably take the form of a fuser roll, pressure roll or release agent donor roll containing an overcoating of a grafted titamer composition.
As used herein, the term grafted titamer refers to a composition comprised of substantially uniform integral interpenetrating networks of haloelastomer, titanium oxide, and polyorganosiloxane, wherein both the structure and the composition of the haloelastomer, titanium oxide, and polyorganosiloxane are substantially uniform when viewed through different slices of the fuser member. The grafted titamer may contain in embodiments other compounds or derivatives thereof disclosed herein including, for example, an amine coupler compound.
The phrase interpenetrating network refers to the intertwining of the haloelastomer, titanium oxide and polyorganosiloxane polymer strands for the grafted titamer.
In a typical electrostatographic reproducing apparatus, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of electroscopic thermoplastic resin particles which are commonly referred to as toner. The visible toner image is then in a loose powdered form and can be easily disturbed or destroyed. The toner image is usually fixed or fused upon a support which may be the photosensitive member itself or other support sheet such as plain paper.
The use of thermal energy for fixing toner images onto a support member is well known. To fuse electroscopic toner material onto a support surface permanently by heat, it is necessary to elevate the temperature of the toner material to a point at which the constituents of the toner material coalesce and become tacky. This heating causes the toner to flow to some extent into the fibers or pores of the support member. Thereafter, as the toner material cools, solidification of the toner material causes the toner material to be firmly bonded to the support.
Typically, the thermoplastic resin particles are fused to the substrate by heating to a temperature of between about 90.degree. C. to about 160.degree. C. or higher depending upon the softening range of the particular resin used in the toner. It is undesirable, however, to raise the temperature of the substrate substantially higher than about 200.degree. C. because of the tendency of the substrate to discolor at such elevated temperatures, particularly when the substrate is paper.
Several approaches to thermal fusing of electroscopic toner images have been described in the prior art. These methods include providing the application of heat and pressure substantially concurrently by various means: a roll pair maintained in pressure contact; a belt member in pressure contact with a roll; and the like. Heat may be applied by heating one or both of the rolls, plate members or belt members. The fusing of the toner particles takes place when the proper combination of heat, pressure and contact time are provided. The balancing of these parameters to achieve the fusing of the toner particles is well known in the art, and they can be adjusted to suit particular machines or process conditions.
During operation of a fusing system in which heat is applied to cause thermal fusing of the toner particles onto a support, both the toner image and the support are passed through a nip formed between the roll pair, or plate or belt members. The concurrent transfer of heat and the application of pressure in the nip, effects the fusing of the toner image onto the support. It is important in the fusing process that no offset of the toner particles from the support to the fuser member takes place during normal operations. Toner particles offset onto the fuser member may subsequently transfer to other parts of the machine or onto the support in subsequent copying cycles, thus increasing the background or interfering with the material being copied there. The so called "hot offset" occurs when the temperature of the toner is raised to a point where the toner particles liquefy and a splitting of the molten toner takes place during the fusing operation with a portion remaining on the fuser member. The hot offset temperature or degradation of the hot offset temperature is a measure of the release property of the fuser roll, and accordingly it is desired to provide a fusing surface which has a low surface energy to provide the necessary release. To ensure and maintain good release properties of the fuser roll, it has become customary to apply release agents to the fuser roll during the fusing operation. Typically, these materials are applied as thin films of, for example, silicone oils to prevent toner offset.
Particularly preferred fusing systems take the form of a heated cylindrical fuser roll having a fusing surface which is backed by a cylindrical pressure roll forming a fusing nip there between. A release agent donor roll is also provided to deliver release agent to the fuser roll. While the physical and performance characteristics of each of these rolls, and particularly of their functional surfaces are not precisely the same depending on the various characteristics of the fusing system desired, the same classes of materials are typically used for one or more of the rolls in a fusing system in a electrostatographic printing system.
One fusing system involved the use of silicone elastomer fusing surfaces, such as a roll with a silicone oil release agent which could be delivered to the fuser roll by a silicone elastomer donor roll. The silicone elastomers and silicone oil release agents used in such systems are described in numerous patents and are fairly collectively illustrated in, for example, U.S. Pat. No. 4,777,087 to Heeks et al. While highly successful in providing a fusing surface with a very low surface energy to provide excellent release properties to ensure that the toner is completely released from the fuser roll during the fusing operation, these systems suffer from a significant deterioration in physical properties over time in a number of fusing environments. In particular, the silicone oil release agent tends to penetrate the surface of the silicone elastomer fuser members resulting in swelling of the body of the elastomer causing major mechanical failure including debonding of the elastomer from the substrate, softening and reduced toughness of the elastomer causing it to chunk out and crumble, contaminating the machine and providing non-uniform delivery of release agent. Furthermore, as described in U.S. Pat. No. 4,777,087, additional deterioration of physical properties of silicone elastomers results from the oxidative crosslinking, particularly of a fuser roll at elevated temperatures.
A more recent development in fusing systems involves the use of fluoroelastomers as fuser members which have a surface with a metal containing filler. The polymeric release agents having functional groups interact with the metal containing filler in the fluoroelastomer surface. Such fusing systems, fusing members and release agents, are described in U.S. Pat. No. 4,264,181 to Lentz et al., U.S. Pat. No. 4,257,699 to Lentz and U.S. Pat. No. 4,272,179 to Seanor, the disclosures of which are totally incorporated by reference. Typically, the fluoroelastomers are (1) copolymers of vinylidenefluoride and hexafluoropropylene, and (2) terpolymers of vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene. Commercially available materials include: Viton E430, Viton GF and other Viton designations as Trademarks of E.I. Dupont deNemours, Inc. as well as the Fluorel materials of 3M Company. The preferred curing system for these materials is a nucleophilic system with a bisphenol crosslinking agent to generate a covalently crosslinked network polymer formed by the application of heat following basic dehydrofluorination of the copolymer. Exemplary of such a fuser member is an aluminum base member with a poly(vinylidenefluoridehexafluoropropylene) copolymer cured with a bisphenol curing agent having copper oxide or lead oxide filler dispersed therein and utilizing a mercapto functional polyorganosiloxane oil as a release agent. The use of polymeric release agents having functional groups which interact with a fuser member to form a thermally stable, renewable self-cleaning layer having release properties for electroscopic thermoplastic resin toners is described in U.S. Pat. No. 4,029,827 to Imperial et al., U.S. Pat. No. 4,101,686 to Strella et al. and U.S. Pat. No. 4,185,140 also to Strella et al., the disclosures of which are totally incorporated by reference.
However, a significant problem of the fluoroelastomer/metal oxide material such as Viton/copper oxide is its relative instability against certain charge control additives which reduces the life of the fusing components, especially for fusing of colored toner. Thus, there is a need for a fusing component material which exhibits one or more of the following characteristics: superior toughness, excellent wear resistance, excellent release capability, and degradation resistance against charge control additives.
Various compositions for components of fuser members are known as illustrated by: Badesha et al., U.S. Pat. No. 5,141,788; Eddy et al., U.S. Pat. No. 5,017,432; Henry, "Fuser Roll Coatings," Xerox Disclosure Journal, Vol. 4, No. 6, p. 821 (November/December 1979); and Badesha et al., U.S. Pat. No. 5,166,031.
Compositions containing organic and inorganic components and processes for the preparation thereof include: Badesha et al., U.S. Pat. No. 5,116,703; Yu, U.S. Pat. No. 5,013,624; Badesha et al., U.S. Pat. No. 4,917,980; Santoso et al., U.S. Pat. No. 4,400,434; Bjerk et al., U.S. Pat. No. 4,051,100; Marzocchi, U.S. Pat. No. 3,775,163; Miller, U.S. Pat. No. 3,663,842, Lentz et al., "Filler Treatments For Thermally Conductive Silicone Elastomers," Xerox Disclosure Journal, Vol. 5, No. 5, pp. 493-94 (September/October 1980); Wilkes et al., "`Ceramers`: Hybrid Materials Incorporating Polymeric/Oligomeric Species Into Inorganic Glasses Utilizing A Sol-Gel Approach", ACS Polymer Reprints, Vol. 26 (2), pp. 300-301 (1985); Lin et al., U.S. Pat. No. 4,743,503; and Kirby et al., U.S. Pat. No. 5,196,228.
Badesha et al., U.S. Ser. No. 08/044,870, filed Apr. 8, 1993 (Attorney Docket No. D/92067), discloses a fuser member comprising a supporting substrate and a layer comprised of integral interpenetrating networks of haloelastomer and silica.
Badesha et al., U.S. Ser. No. 08/044,860, filed Apr. 8, 1993 (Attorney Docket No. D/92067Q), discloses a fuser member comprising a supporting substrate and a layer comprised of integral interpenetrating networks of haloelastomer, silica, and polyorganosiloxane.